Field of Invention
The present invention relates to an exhaust system including a selective catalytic reduction (SCR) catalyst, and more particularly to a method of determining a correcting logic for a reacting model of an SCR catalyst, a method of correcting parameters of the reacting model of the SCR catalyst and an exhaust system using the same that corrects the parameters of the reacting model through sensitivity analysis of the reacting model which defines reaction of the SCR catalyst.
Description of Related Art
Generally, exhaust gas flowing out from an engine through an exhaust manifold is urged into a catalytic converter mounted at an exhaust pipe and is purified therein. After that, the noise of the exhaust gas is decreased while passing through a muffler and the exhaust gas is then emitted into the air through a tail pipe. The catalytic converter purifies pollutants contained in the exhaust gas. In addition, a particulate filter for trapping particulate matter (PM) contained in the exhaust gas is mounted in the exhaust pipe.
A selective catalytic reduction (SCR) catalyst is one type of such a catalytic converter. Reducing agent such as urea, ammonia, carbon monoxide and hydrocarbon (HC) reacts better with nitrogen oxide than with oxygen in the SCR catalyst.
An exhaust system of a vehicle provided with the SCR catalyst includes an urea tank and dosing module. The dosing module injects reducing agent such as urea into the exhaust gas passing through the exhaust pipe, and thereby the SCR catalyst purifies the nitrogen oxide efficiently.
The reducing agent injected from the dosing module is absorbed in the SCR catalyst, is released if the exhaust gas containing the nitrogen oxide passes through the SCR catalyst, and reacts with the nitrogen oxide. If excessive reducing agent is injected from the dosing module, a portion of the reducing agent is not absorbed in the SCR catalyst and is slipped. Ammonia is typically used as the reducing agent of the SCR catalyst. If the ammonia is slipped from the SCR catalyst, the slipped ammonia may cause stink and customers may have complaints. If the dosing module injects the reducing agent insufficiently, the nitrogen oxide contained in the exhaust gas cannot be sufficiently removed and is exhausted to the exterior of the vehicle. Therefore, amount of the reducing agent injected from the dosing module should be precisely controlled.
In a conventional method of determining the amount of the reducing agent, the amount of the reducing agent according to driving conditions is stored in a map through experiments and the amount of the reducing agent according to current driving condition is determined from the map. However, since there are a millions of driving conditions affecting the amount of the reducing agent, manufacturing the map is a tedious and expensive process.
In addition, since the driving condition changes very quickly, a measuring apparatus has error, and experiments cannot be conducted under all the driving conditions when manufacturing the map, the map itself has error. In order to reduce the errors, the map is corrected. However, it is very difficult to get over innate limitations such as error of the measuring apparatus and quick change of the driving condition.
Recently, researches for predicting reaction of an SCR catalyst using a reacting model of the SCR catalyst and determining injection amount of the reducing agent using the predicted results are in progress. Because the reacting model of the SCR catalyst is also determined through experiments or analysis, error exists between an actual value and a predicted value. In addition, since the conventional method of correcting the map is hard to be applied to a method of correcting the reacting model, it is demanded to develop a method of correcting the reacting model.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.